Method for estimating position where abnormality has occurred, and program for estimating position where abnormality has occurred

Abstract

A method estimates a position where an abnormality has occurred. The method for estimating a position where an abnormality has occurred in a robot includes an abnormality detection step of detecting occurrence of an abnormality, and a position detection step of detecting a position where the abnormality has occurred when the occurrence of the abnormality is detected in the abnormality detection step.

The invention claimed is: 
     
       1. A method for estimating a position where an abnormality has occurred in a robot that drives an arm using a servo motor, the method comprising:
 an abnormality detection step of detecting that an abnormality has occurred; 
 a position detection step of detecting, when occurrence of the abnormality is detected in the abnormality detection step, a position where the abnormality has occurred; 
 a cycle observed value detection step of observing a transition of a value of a current flowing through the servo motor or a position deviation of the servo motor as an observed value, and detecting a representative value of the observed value for each cycle in a prescribed operation of an operation for each cycle in an operation repeatedly performed by the robot; and 
 a daily observed value detection step of detecting a representative value of the observed value for each day from the representative value of the observed value detected for each cycle, wherein 
 when the representative value of the observed value for each day deviates from a prescribed range, the occurrence of the abnormality is detected in the abnormality detection step. 
 
     
     
       2. The method for estimating a position where an abnormality has occurred according to  claim 1 , wherein the position detection step includes an estimation step of estimating a position where the abnormality has occurred from a type of value deviating from the prescribed range of the representative value of the observed value for each day detected for a plurality of types, and a waveform of the observed value when the occurrence of the abnormality is detected in the abnormality detection step. 
     
     
       3. The method for estimating a position where an abnormality has occurred according to  claim 2 , wherein
 the position where the abnormality has occurred is organized on a table in advance in accordance with the type of value deviating from the prescribed range and the waveform of the observed value when the occurrence of the abnormality is detected in the abnormality detection step, and 
 the position where the abnormality has occurred is estimated by referring to the table in the estimation step. 
 
     
     
       4. The method for estimating a position where an abnormality has occurred according to  claim 2 , wherein
 in the cycle observed value detection step, a mean square value and a peak value of the observed value in the prescribed operation are calculated for each cycle, and 
 the daily observed value detection step includes:
 a mean square median calculation step of calculating a median of the mean square value for each day, 
 a mean square standard deviation calculation step of calculating a standard deviation of the mean square value for each day, 
 a peak median calculation step of calculating a median of the peak value for each day, and 
 a peak standard deviation calculation step of calculating a standard deviation of the peak value for each day. 
 
 
     
     
       5. The method for estimating a position where an abnormality has occurred according to  claim 4 , wherein the occurrence of the abnormality is detected in the abnormality detection step, when any one of values deviates from a prescribed range, the values being the median of the mean square value calculated in the mean square median calculation step, the standard deviation of the mean square value calculated in the mean square standard deviation calculation step, the median of the peak value calculated in the peak median calculation step, and the standard deviation of the peak value calculated in the peak standard deviation calculation step. 
     
     
       6. The method for estimating a position where an abnormality has occurred according to  claim 2 , wherein the estimation step includes a selection step of selecting which pattern among a plurality of preset patterns of the waveform of the observed value at detection of the occurrence of the abnormality in the abnormality detection step is applicable to. 
     
     
       7. The method for estimating a position where an abnormality has occurred according to  claim 6 , wherein
 the observed value is a value of a current flowing through the servo motor, 
 in the selection step, pattern  1  is defined when the waveform of the current flowing through the servo motor at detection of the occurrence of the abnormality in the abnormality detection step is enlarged similarly to a reference waveform of the current flowing through the servo motor without the occurrence of the abnormality, and an enlargement ratio is equal to or less than a threshold, pattern  2  is defined when the enlargement ratio is greater than the threshold, pattern  3  is defined when there is a frequency at which a component of the waveform of the current flowing through the servo motor is larger than the reference waveform by a certain amount or more, and the frequency is within a prescribed frequency range, and pattern  4  is defined when the frequency is not within the prescribed frequency range, and 
 the selection step includes a current value pattern selection step of selecting which one of patterns  1  to  4  the waveform of the current flowing through the servo motor at detection of the occurrence of the abnormality in the abnormality detection step is applicable to. 
 
     
     
       8. The method for estimating a position where an abnormality has occurred according to  claim 6 , wherein
 the observed value is a position deviation of the servo motor, 
 in the selection step, pattern  5  is defined when there is a frequency at which a component of the waveform of the position deviation of the servo motor at detection of the occurrence of the abnormality in the abnormality detection step is larger than a reference waveform of the position deviation of the servo motor without the occurrence of the abnormality by a certain amount or more, and the frequency is within a prescribed frequency range, and pattern  6  is defined when the frequency is not within the prescribed frequency range, and 
 the selection step includes a position deviation pattern selection step of selecting which one of patterns  5  and  6  the waveform of the position deviation of the servo motor at detection of the occurrence of the abnormality in the abnormality detection step is applicable to. 
 
     
     
       9. A non-transitory computer readable medium storing thereon a program for estimating a position where an abnormality has occurred in a robot that drives an arm using a servo motor, the program causing a computer to execute:
 an abnormality detection step of detecting that an abnormality has occurred; 
 a position detection step of detecting, when occurrence of the abnormality is detected in the abnormality detection step, a position where the abnormality has occurred; 
 a cycle observed value detection step of observing a transition of a value of a current flowing through the servo motor or a position deviation of the servo motor as an observed value, and detecting a representative value of the observed value for each cycle in a prescribed operation of an operation for each cycle in an operation repeatedly performed by the robot; and 
 a daily observed value detection step of detecting a representative value of the observed value for each day from the representative value of the observed value detected for each cycle, wherein 
 when the representative value of the observed value for each day deviates from a prescribed range, the occurrence of the abnormality is detected in the abnormality detection step.